Method of forming a casting mold pattern

ABSTRACT

A method of forming a casting mold pattern that includes a core comprises mounting the core in a fixture such that the core is free of flexing imposed by the fixture. Material is removed from and/or added to a first and/or second mounting surface of the core. The core is then positioned in a die, and wax is conducted into the die to form the pattern. The amount of material removed from the first and/or second mounting surface is such that the core will be within a predetermined range of acceptable positions when the core is in the die with the first mounting surface engaging a first core locating surface of the die end with the second mounting surface engaging a second core locating surface of the die. The range of acceptable positions is determined relative to an ideal position of an ideal core.

FIELD OF THE INVENTION

The present invention relates to a method of forming a casting moldpattern that includes a core and, more particularly, to a method offorming a casting mold pattern in which a core can be disposed in anacceptable position in a pattern forming die by removing material fromand/or adding material to the core.

BACKGROUND OF THE INVENTION

Articles, such as turbine blades or airfoils, have been formed by a lostwax investment casting process. The process includes forming a patternhaving the configuration of a space or cavity to be formed in a mold inwhich an article is to be cast. A core portion of the pattern has aconfiguration corresponding to the configuration of a space to be formedin the article itself.

To form the casting mold pattern, the core is positioned in a diecavity. Wax is injected into the die cavity around the core. Theresulting pattern is subsequently covered with a ceramic mold material.

Once the pattern has been covered with a ceramic mold material, the waxportion of the pattern is melted. The wax is removed from the mold toleave a cavity into which metal is cast. The core is at least partiallyenclosed by the cast metal. The core is subsequently removed to formspace in the cast metal article. The space formed by the core may be acomplex arrangement of passages.

Cores for casting mold patterns used to manufacture articles such asairfoils may experience twisting during the core manufacturing process.A core that experiences such twisting may not be usable to form apattern to create a mold in which an article such as an airfoil is to becast.

SUMMARY OF THE INVENTION

The present invention is directed to a method of forming a casting moldpattern that includes a core and, more particularly, to a method offorming a casting mold pattern in which a core can be disposed in anacceptable position in a pattern forming die by removing material fromand/or adding material to the core.

In accordance with an embodiment of the present invention, a method isprovided of forming a casting mold pattern that includes a core. Thecore has a length, a first end, and a second end. The second end isspaced apart from the first end by the length. The core also has a firstmounting surface adjacent the first end of the core and a secondmounting surface adjacent the second end of the core. The methodcomprises the steps of (a) removing material from and/or adding materialto the first mounting surface and/or the second mounting surface; and(b) positioning the core in a pattern forming die after removingmaterial from and/or adding material to the first mounting surfaceand/or the second mounting surface. The pattern forming die has a firstcore locating surface to support the first end of the core and a secondcore locating surface to support the second end of the core. The core ispositioned in the pattern forming die with the first mounting surface inengagement with the first core locating surface and with the secondmounting surface in engagement with the second core locating surface.The method further comprises the step of conducting a flow of wax intothe pattern forming die to form a casting mold pattern while the core ispositioned in the pattern forming die with the first mounting surface inengagement with the first core locating surface and with the secondmounting surface in engagement with the second core locating surface.The material removed from the first mounting surface and/or the secondmounting surface is in an amount such that the core will be within apredetermined range of acceptable positions when the core is positionedin the pattern forming die with the first mounting surface in engagementwith the first core locating surface and with the second mountingsurface in engagement with the second core locating surface. Thepredetermined range of acceptable positions is determined relative to anideal position in the pattern forming die of an ideal core.

In accordance with another embodiment of the present invention, a methodis provided for adjusting a core to be at least partially covered by waxto produce a casting mold pattern. The core has a length, a first end,and a second end. The second end is spaced apart from the first end bythe length. The core also has a first mounting surface adjacent thefirst end of the core and a second mounting surface adjacent the secondend of the core. The method comprises the steps of (a) mounting the corein a fixture such that the core is free of any flexing along the lengthof the core imposed by the fixture and (b) removing material from thefirst mounting surface and/or the second mounting surface. The materialbeing removed from the first mounting surface and/or the second mountingsurface is in an amount such that the core will be within apredetermined range of acceptable positions when the core is positionedin a pattern forming die with the first mounting surface in engagementwith a first core locating surface of the pattern forming die and withthe second mounting surface in engagement with a second core locatingsurface of the pattern forming die. The predetermined range ofacceptable positions is determined relative to an ideal position in thepattern forming die of an ideal core with an ideal twist along itslength.

In accordance with a further embodiment of the present invention, afixture is provided for adjusting a core to be at least partiallycovered by wax to produce a casting mold pattern. The core has a length,a first ends and a second end. The second end is spaced apart from thefirst end by the length. The core also has a first mounting surfaceadjacent the first end of the core and a second mounting surfaceadjacent the second end of the core. The fixture comprises (a) a firstgripping device configured and dimensioned to grip the core adjacent itsfirst end and (b) a second gripping device configured and dimensioned togrip the core adjacent its second end. The first gripping device isspaced apart from the second gripping device and is able to rotaterelative to the second gripping device. The fixture also comprises alocking device for locking the first gripping device against rotationrelative to the second gripping device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the present inventionwill become apparent to one skilled in the art upon consideration of thefollowing description of the invention and the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a core for use in forming a pattern toproduce a die for a lost wax investment casting;

FIG. 2 is a schematic sectional view of the core of FIG. 1 positioned ina die for forming a pattern;

FIG. 3 is a schematic sectional view of a pattern formed around the coreof FIG. 1 as positioned in the die of FIG. 2;

FIG. 4 is a schematic sectional view of a mold formed around the patternand core of FIG. 3;

FIG. 5 is a schematic sectional view of the mold of FIG. 4 with thepattern removed and the core remaining;

FIG. 6 is a schematic illustration of a prior art die that incorporatesmechanisms for positioning a core in the die;

FIG. 7 is an elevation view of a fixture for holding a core to permitselective removal of material from the core;

FIG. 8 is a plan view of the fixture of FIG. 7;

FIG. 9 is a perspective view of a portion of the fixture of FIG. 7;

FIG. 10 is a perspective view of a core mounted in the fixture of FIG.7;

FIG. 11 is a schematic illustration of another die that is free anymechanism for positioning a core in the die; and

FIG. 12 is a flow chart of a method of forming a pattern such as thepattern of FIG. 3.

DETAILED DESCRIPTION

FIG. 1 illustrates a core 10 for use in forming a casting mold pattern12 (FIG. 3), in accordance with an example of the present invention. Theillustrated core 10 and pattern 12 are configured to form a mold forfabricating or casting a high pressure turbine blade (not shown) for agas turbine engine or jet engine (not shown). More particularly, thepattern 12 has the configuration of a space or cavity to be formed in amold 76 (FIGS. 4 and 5) in which such a high pressure turbine blade (notshown) is to be cast. The core 10 has a configuration that correspondsto the configuration of a cavity in such a high pressure turbine blade.The core 10 and pattern 12 may, however, be configured to form othercomponents of a gas turbine engine or jet engine, such as other turbineblades, airfoils, and blade outer air seals, which have internalcavities. The gas turbine engine may be used, for example, as apropulsion device for a vehicle, such as an airplane, or as a powergenerating device in a stationary power plant. More generally, thepattern 12 and the core 10 may be configured to form a mold forfabricating any article that has an internal cavity and that is formedby a lost wax investment casting process.

The core 10 may be made of any suitable material. The illustrated coreis made of a known ceramic material, which may have a compositionsimilar to the composition of the core disclosed in U.S. Pat. No.5,580,837. The core 10 may, however, be made of different materials andmay have different compositions, including, for example, the compositiondisclosed in U.S. Pat. No. 4,583,581. When the core 10 is to be used informing a ceramic mold for casting of gas turbine engine components, thecore 10 may be made of a ceramic material that is compatible with theceramic material forming the mold. The core 10 may have any one of manydifferent configurations, including, for example, the configurationsillustrated in U.S. Pat. No. 5,580,337 and U.S. Pat. No. 5,599,166. Thecore 10 may be molded using any of several different known moldingtechniques including, but not limited to, injection molding, transfermolding, compression molding, die pressing, and extrusion, and maythereafter be fired at an elevated temperature, such as 2,000° F. to3,000° F., to develop the strength required for the core's intended use.

The core 10 is made in one piece and has a root end 13, an adjacent rootend portion 14, a tip end 15, and an adjacent tip end portion 16. Theroot end 13 is spaced apart from the tip end 15 by the length of thecore 10. The root end portion 14 includes a first mounting surface 18.As shown, the first mounting surface 18 includes two optional datum pads20, which may be circular portions of the first mounting surface raisedabove the level of the remainder of the first mounting surface 18. Thetwo datum pads 20 effectively function as two mounting surfaces, as willbecome apparent from the description below. The first mounting surface18 may not have any raised datum pads 20, may have more or fewer thantwo raised datum pads 20, or may have depressions with bottom surfacesbelow the level of the remainder of the first mounting surface. The tipend portion 16 includes a second mounting surface 22.

A body portion 24 of the core 10 extends lengthwise or along the lengthof the core from the root end portion 14 to the tip end portion 16. Thebody portion 24 of the core 10 includes an airfoil portion 26, whichextends for only pad of the length of the body portion. When viewed incross-section taken perpendicular to the length of the core 10, as shownschematically in FIG. 2, the airfoil portion 26 has an arcuatecross-sectional configuration. The airfoil portion 26 of the core 10thus has a convex major side surface 28 and a concave major side surface30 (FIG. 2), which is spaced apart from and presented in a directionaway from the convex major side surface. The airfoil portion 26 also hasa leading edge 32 and a trailing edge 34, as does the tip end portion16. Each of the convex major side surface 28 and the concave major sidesurface 30 of the airfoil portion 26 has a configuration that is afunction of the desired configuration of a cavity to be formed in thehigh pressure turbine blade (not shown). The convex major side surface28 of the airfoil portion 26 also corresponds to the first mountingsurface 18 of the root end portion 14 and to the second mounting surface22 of the tip end portion 16.

Holes or openings 36 may be formed in the core 10. The holes or openings30 extend entirely through the body portion 24 and the airfoil portion26 of the core 10 from the convex major side surface 28 to the concavemajor side surface 30. The holes or openings 36 may be in the form ofelongated slots 38, as shown in FIG. 1. The slots 38 may extend forsubstantially the entire length of the body portion 24 of the core 10from the root end portion 14 to the tip end portion 16. Alternatively,the slots 38 may extend for only part of the entire length of the bodyportion 24, such as, for example, the length of the airfoil portion 26of the core 10. Elongated sections 37 of the core 10 separate the slots38 from one another. The elongated sections 37 may be joined to oneanother, as shown adjacent the tip end portion 16 of the core 10 inFIG. 1. The elongated sections 37 may also be joined to and supported byeither or both the tip end portion 16 and the root end portion 14s as isalso shown in FIG. 1. Although the holes or openings 36 are shown inFIG. 1 as slots 38, the holes or openings 36 may have slotconfigurations other than the specific configurations of the slots 38shown in FIG. 1 or configurations other than slots.

Like the core 10, the casting mold pattern 12 has an arcuatecross-sectional configuration. The pattern 12 thus has a convex majorouter side surface 40 and a concave major outer side surface 42, whichis spaced apart from and presented in a direction away from the convexmajor side surface. The pattern 12 also has a leading edge 44 and atrailing edge 46. Each of the convex major outer side surface 40 and theconcave major outer side surface 42 of the pattern 12 has aconfiguration that is a function of the desired configuration of acorresponding outer surface of the high pressure turbine blade (notshown) that is to be cast The pattern 12 further has a convex majorinner side surface 48 and a concave major inner side surface 50. As canbe seen in FIG. 2, the convex major inner side surface 48 abuts and isdefined by the concave major side surface 30 of the core 10. The convexmajor inner side surface 48 also extends generally parallel to theconcave major outer side surface 42 of the pattern 12. Similarly, theconcave major inner side surface 50 of the pattern 12 abuts and isdefined by the convex major side surface 28 of the core. The concavemajor inner side surface 50 of the pattern 12 also extends generallyparallel to the convex major outer side surface 40 of the pattern.

The core 10 is used to form the pattern 12 by positioning the core in adie 60. The die 60, which is shown schematically in FIGS. 2 and 3,includes a first die section 62 and a second die section 64, which aremovable relative to one another. The first die section 62 has a firstdie surface 66 configured to form the convex major outer side surface 40of the pattern 12. The second die section 64 has a second die surface 68configured to form the concave major outer side surface 42 of thepattern 12. When the first die section 62 and the second die section 64are moved into contact with one another adjacent their outer peripheriesto close the die 60, the first and second die surfaces 66 and 68 remainspaced apart from one another to define a die cavity 70. When the core10 is positioned in the die 60 and the die is closed, the core occupiesa portion of the die cavity 70. The remainder of the die cavity 70 isthe space in which the pattern 12 is formed.

To form the pattern 12, the core 10 is positioned in the die 60 and thedie is closed. A known natural or artificial wax 72 is introduced intothe die cavity 70 through an inlet passage (not shown) formed in the die60. The wax 72 at least partially covers the core 10 and fills the holesor openings 36 in the core. When the wax 72 hardens, the wax at leastpartially encloses the core 10 and forms the portion of the pattern 12not formed by the core. After the wax 72 hardens, the die 60 is opened,and the pattern 12 is removed from the die. Thereafter, the pattern 12is at least partially enclosed or invested with a suitable investment ormold material 74 (FIG. 4). For example, the pattern 12 may be coatedwith multiple layers of a slurry formed of a ceramic material. Theslurry coats and ultimately at least partially encloses the pattern 12.The slurry then solidifies over the outside of the pattern 12 to form acasting mold 76,

To provide a cavity for casting the high pressure turbine blade, the wax72 forming the pattern 12 is removed from the mold 76 by, for example,melting the wax. The core 10, however, remains in the mold. The cavityresulting from the removal of the wax is filled with a molten metal,which solidifies around the core 10 to form the high pressure turbineblade (not shown). The core 10 is subsequently removed from the highpressure turbine blade to provide cooling passages or other space in theturbine blade. More particularly, the openings 36 in the form of slots38 in the core permit the flow of metal to result in metal supportsconnecting opposite sides of the high pressure turbine blade (notshown), while the elongated sections 37, when removed, will result inpassages, such as cooling passages, in the high pressure turbine blade.

To produce a pattern 12 that can be used to generate an acceptable mold76 that can, in turn, be used to produce an acceptable turbine blade orother cast article, it is important both to produce an acceptablyconfigured and dimensioned core 10 and also to position the core 10 inan acceptable orientation and location in the die 60 for producing thepattern. Among other things, a core must include a certain amount ordegree of twist because the gas turbine blade that will ultimately befabricated using the core must have a certain amount or degree of twistin order to function properly. One type of core deviation arises fromeither excessive or insufficient twist in the core, which can alsoaffect the camber of the core.

Broadly, the twist of the core and the gas turbine blade relates to theorientation of a chord line or axis defined by the cross-section of thecore and the cross-section of the gas turbine blade, respectively,relative to an axis that extends generally along the length of the coreand the gas turbine blade. As indicated in FIG. 1, an axis 100 extendsfrom the root end 13 of the core 10 to the tip end 15, which is alongthe length of the core 10. More particularly, the axis 100 extendsradially outward from an axis of rotation of a gas turbine (not shown)in which the turbine blade (not shown) to be fabricated using the coreis mounted. As indicated in FIG. 2, a chord line or axis 102 extendsbetween the leading edge 32 and the trailing edge 34 of the core 10, insuccessive cross-sections taken along the length of the core 10 from theroot end portion 14 to the tip end portion 16, the arcuate lengths ofthe convex and concave major side surfaces 23 and 30 of the coreincrease, and the angular position of the chord line or axis 102relative to the axis 100 changes. The camber of the core and the gasturbine blade relates to the curvature of the camber line 104 or theaxis extending along the geometric centerline of the cross-section ofthe core. If an actual core 10 is produced with too much twist or toolittle twist as compared to the twist of a theoretical as-designed orideal core or if the actual core is produced with too much or too littlecamber, it may not be possible to position the actual core in a die,such as the die 80, in a position adequate to produce an acceptablepattern 12 and thus an acceptable mold 76.

Various techniques and mechanisms have been proposed for producingcores, such as core 10, within acceptable shape and dimensionaltolerances, and various techniques and mechanisms have also beenproposed for positioning a core in a die to produce a pattern withinacceptable shape and dimensional tolerances. Recognizing that individualcores produced by commercially viable manufacturing techniques orprocesses vary from a theoretical or ideal core, one technique and anassociated mechanism for positioning a core in a die is shown in FIG. 6and is disclosed in greater detail in U.S. Pat. No. 7,913,743.

As shown in FIG. 6, a core, such as the core 10, is positioned in a die,such as die 60, in an orientation in which the airfoil portion 26 of thecore is inverted as compared to the orientation shown in FIG. 2.Specifically, the concave major side surface 30 of the airfoil portion26 is presented in an upward direction, as viewed in FIG. 6, and ispositioned above the convex major side surface 28. The convex major sidesurface 23 of the airfoil portion 26 of the core 10 is spacedappropriately relative to or away from the first die surface 66 of thefirst die section 82 by core positioning members 78. Each corepositioning member 78 includes a core locating surface 80. The foregoinggeneral description is common to both the die 60 shown in FIG. 6 and thedie 80a shown in FIG. 7.

In the die 60 shown schematically in Fig, 8, each core positioningmember 78 is an elongated pin or shaft that has a core locating surface80 at or adjacent to an upper end or tip of the pin or shaft. Five corepositioning members 78 are shown in a line or row under the airfoilportion 26 of the core 10 to position the core 10 in a verticaldirection relative to the first die surface 66. In addition, a sixthcore positioning member 78 is shown adjacent the leading edge 32 of theairfoil portion 26 to position the core 10 laterally (to the left andright, as viewed in FIG. 6) relative to the first die surface 86. Agreater or lesser number of core positioning members 78 may be used toposition the core 10 relative to the die 60.

Each core positioning member 78 is associated with a reversible drivemotor 82 so that the core positioning member may be moved in oppositeaxial directions, which are either upward and downward or left andright, as viewed in FIG. 6. Each individual core positioning member 78is operatively connected to a corresponding individual drive motor 82 bya reversible drive train 84. The drive trains 84 may have any desiredconstruction. The illustrated drive trains 84 have internally threadedmembers that are disposed in engagement with externally threadedmembers. The internally threaded members may be connected with the drivemotors 82 through suitable reduction gearing. The externally threadedmembers are connected with the core positioning members 78. Rather thanusing internal and external thread convolutions to effect movement ofthe core positioning members 78, the drive trains 84 may have camsurfaces to move the core positioning members relative to the first diesurface 66 of the first die section 62 of the die 60.

The drive motors 82 are controlled by a controller 86, which may be amicroprocessor or, as shown schematically in FIG. 6, a computer with adisplay 88 and an internal memory 90. Communication between thecontroller 86 and each drive motor 82 may be via wires 92, as shown inFIG. 6, or may be wireless. Operation of the drive motors 82 by thecontroller 86 may be based on information about the individual actualcore 10 being positioned in the die 60, as well as information andcalculations regarding the configuration and dimensions of a theoreticalor ideal core and the theoretical or ideal pattern to be produced usingsuch an ideal core. Thus, as described in greater detail in U.S. Pat.No. 7,913,743, the actual core 10 may be scanned with a laser-based or amechanical probe-based coordinate measuring machine to measure theactual dimensions and configuration of the core. This information maythen be used by the controller 86 to determine, using commerciallyavailable software, a best fit spatial relationship of the actual core10 to a spatial envelope for an ideal core and/or to the die 80 and thedie cavity 70 and thereafter to operate the drive motors 82 to adjustthe positions of core locating surfaces 80 of the core positioningmembers 78 relative to the first die surface 66 of the die 60 to placethe actual core 10 in the calculated best fit spatial relationship.Thus, drive motors 82 may be operated to move the core positioningmembers 78 to positions in which the core locating surfaces 80 areoffset from the positions in which they would be disposed if the core 10had the dimensions and configurations of an ideal core.

Although the use of best fit software and a die with adjustable corepositioning members, such as the core positioning members 78 of the core60 shown in FIG. 6, can permit the production of an acceptable pattern12 and thus an acceptable mold 76 with an actual core 10 produced withtoo much twist or too little twist as compared to the twist of atheoretical, as-designed or ideal core, the use of best fit software anda die with adjustable core positioning members can be time consuming andexpensive. The present invention reflects the discovery that coresproduced with a twist that is greater or less than the twist of atheoretical, as-designed or ideal core can be used to produce acceptablepatterns, such as the pattern 12, without investing the time and costinvolved with best fit software and/or a die with adjustable corepositioning members. In particular, a core, such as the core 10, may heallowed to assume an unflexed or unstressed condition in a fixture orjig and, when the core is in its unflexed condition, anempirically-determined amount of material may be removed from or addedto one or both of the first mounting surface 18 of the root end portion14 of the core 10 and the second mounting surface 22 of the tip endportion 16 of the core. After removing material from or adding materialto the first mounting surface 18 and/or the second mounting surface 22,the core 10 may then be placed in a die in which the core positioningmembers are fixed in position to produce an acceptable pattern, such asthe pattern 12, without best fit software and/or a die with adjustablecore positioning members.

In accordance with an embodiment of the invention, as shown in FIGS. 7through 10, a fixture 110 is provided in which or into which a core 10may be mounted so that at least one of the first and second mountingsurfaces 13 and 22 is positioned and presented in a location andorientation in which the required amount of material can be removedand/or added by causing a tool to move along a predetermined path. Moreparticularly, the fixture 110 is constructed such that the core 10 maybe mounted in a manner first to permit the core to assume an unstressedor unflexed condition and then to hold the core in its unstressed orunflexed condition for material removal and/or addition.

The fixture 110 comprises a first gripping device 112 and a secondgripping device 114, which is spaced apart from the first grippingdevice. Both the first gripping device 112 and the second grippingdevice 114 are mounted on a fixture support member or base plate 116. Asshown, the first and second gripping devices 112 and 114 are bothmounted on the base plate 116 in fixed positions. One or both of thefirst and second gripping devices 112 and 114 may, however, be movablymounted on the base plate 116 so that one or both the first and secondgripping devices may be moved, for example, slid, along the base platefrom a first position to a second position and then clamped or locked inthe second position so as to accommodate cores of different lengths.

The second gripping device 114 includes a locator block 118, a clampmechanism 120, and a clamp mounting block 122. The locator block 118engages and is mounted on an upper surface 124 of the base plate 116.The locator block 118 includes a support surface 126 (FIG. 10) that isoriented at an angle to the upper surface 124 of the base plate 116. Thesupport surface 126 receives and supports the tip end portion of a core,such as the tip end portion 16 of the core 10. More particularly, asshown in FIG. 10, a metal edge locator 128 and a metal mounting surfacelocator 130 are attached to the locator block 118 such that they projectoutward and away from the support surface 126. When a core 10 is mountedin the fixture 110, the edge locator 128 receives and engages thetrailing edge 34 of the tip end portion 16 of the core, while themounting surface locator 130 engages the tip end surface 26 of the tipend portion. The mounting surface locator 130 may be attached to thelocator block 118 via a screw thread (not shown) so that the distal end(not shown) of the mounting surface locator may be moved toward and awayfrom the support surface 126 for fine adjustment of the position of acore 10 mounted in the fixture 110. The support surface 126 is orientedat an angle to the upper surface 124 of the base plate 116 so that whenthe tip end portion 16 of the core 10 is supported on the supportsurface and, more specifically, on the edge locator 128 and the mountingsurface locator 130, the root end portion 14 of the core isapproximately horizontal and parallel to the upper surface 124 of thebase plate 116 due to the twist in the core.

The clamp mounting block 122 also engages and is mounted on the uppersurface 124 of the base plate 116. The clamp mounting block 122 has agreater height than the locator block 118 and is located behind and incontact with the locator block. The clamp mounting block 122 alsoincludes a support surface 132 that is oriented at an angle to the uppersurface 124 of the base plate 116. The support surface 132 issubstantially parallel to the support surface 126 of the locator block118. The clamp mechanism 120 is mounted on the support surface 132 ofthe clamp mounting block 122. The clamp mechanism 120 includes a supportbracket 134 secured to the clamp mounting block 122 using fasteners (notshown), such as screws. Three bars or links 136, 138 and 140 of athree-bar linkage are pivotally attached to the support bracket 134 topermit manual clamping and unclamping of the core 10. A handle 142 isattached to one end of the link 136, and a clamp pad 144 is attached toone end of the link 140. When the handle 142 is grasped by an individualand pushed upward toward the position shown in FIG. 10, the clamp pad144 is moved toward the support surface 126 to grip or clamp the tip endportion 16 of a core 10. Conversely, when the handle 142 is pulleddownward away from the position shown in FIG. 10, the clamp pad 144 ismoved away from the support surface 126 to unclamp the tip end portion16 of the core 10. The position of the clamp pad 144 relative to thelink 140 and thus to the support surface 126, when the handle 142 ispushed upward, can be adjusted via a threaded portion of a post 145connecting the clamp pad to the link 140.

As best seen in FIGS. 9 and 10, the first gripping device 112 includes asupport or bearing block 146, a carriage 148, and a locator block orcradle 150. The bearing block 146 engages and is mounted on the uppersurface 124 of the base plate 116 and thus maintains a fixed rotationalposition relative to the second gripping device 114. The carriage 148 ispivotally mounted on the bearing block 146 via a pin or shaft 147 (FIG.7) and a bearing (not shown). The carriage 148 is thus pivotable orrotatable relative to the bearing block 146 and the second grippingdevice 114. To limit the extent to which the carriage 148 can pivotrelative to the bearing block 146 and also relative to the secondgripping device 114, a stop block 152 is mounted on the upper surface124 of the base plate 116 adjacent to the bearing block and below thecarriage, as viewed in FIGS. 9 and 10. The stop block 152 includes agroove or notch 154 that is presented toward and opens toward thecarriage 148. A dowel 156 projects radially outward and away from acurved outer surface 158 of the carriage 148 and is received in thenotch 154. The width of the notch 154 is greater than the diameter orwidth of the dowel 156 so that the dowel can move to a limited extent inthe notch and thus the carriage 148 can pivot to a limited extentrelative to the bearing block 146 and the second gripping device 114. Aset screw 159 can be used to adjust the effective width of the notch154.

The cradle 150 is attached to the carriage 143 for pivotal movement withthe carriage. The cradle 150 includes a support surface 160 and alateral guide surface 162. The support surface 160 is recessed into thecradle 150 so that a U-shaped wall 164 is formed by the cradle aroundthree sides of the support surface. The fourth side of the supportsurface 160 is open to the outer periphery of the cradle 150 and ispresented toward the second gripping device 114. The support surface 160extends for most of the lateral dimension or width of the cradle 150.The lateral guide surface 162 is a portion of the U-shaped wail 164 andextends outward from the U-shaped wall toward the central portion of thesupport surface 160 from one leg or upright of the U-shape. Across theU, projecting through the U-shaped wall 164 toward the lateral guidesurface 162, as viewed in FIG. 9, is a threaded clamping member 166. Theclamping member 166 can be advanced toward the lateral guide surface 162and unscrewed away from the lateral guide surface to enable an article,such as the root end portion 14 of a core 10, to be clamped or guidedbetween the clamping member and the lateral guide surface.

Also attached to the carriage 148 for pivotal movement with the carriageis a clamp arm 168. The clamp arm 168 is pivotally attached at one end170 to the carriage 148. The clamp arm 168 may be pivoted from a first,upright or vertical position substantially in the plane of the carriage148 through approximately 90° into a second, horizontal position (shownin FIGS. 9 and 10) in which the opposite end 172 of the clamp armprojects over, overhangs or overlies the support surface 160 of thecradle 150. A spring plunger 174 extends through the opposite end 172 ofthe clamp arm 168. When the clamp arm 168 is in its second position, asshown in FIG. 9, the spring plunger 174 projects toward the supportsurface 160 to enable an article, such as the root end portion 14 of acore 10, to be gripped or clamped between the spring plunger and thesupport surface. To hold the clamp arm 168 in its second position, ahalf-turn screw member 176, which is mounted on a bracket 178 attachedto the carriage 148, may be turned to a first position in which thehalf-turn screw member overlies the clamp arm 168 and prevents the clamparm from moving to its first, vertical position. To release the clamparm 168 to pivot relative to the carriage 148 into its first position,the half-turn screw member 176 may be rotated through 180° so the clamparm is free to pivot relative to and past the half-turn screw member.

To permit the carriage 148 to be looted in position against pivotalmovement relative to the bearing block 146 and relative to the secondgripping device 114, the fixture 110 includes a locking mechanism ordevice. The locking device includes two shoulder screws 186 that extendthrough the carriage 148 into the bearing block 146. The head 188 ofeach shoulder screw 186 abuts a washer 190 that is in contact with anouter surface 192 of the carriage 148, while the shaft 194 of eachshoulder screw passes through an arcuate slot (not shown) in thecarriage, through a cylindrical bore (not shown) in the bearing block146, and into one of two pancake-style, pneumatic piston-cylinder units184.

The piston-cylinder units 184 are operable to draw the heads 188 of theshoulder screws 186 and thus the washers 190 against the outer surface192 of the carriage 148 to press the carriage against the bearing block146 and lock the carriage in position relative to the bearing block orhold the carriage against pivotal movement relative to the bearing block146 and the second gripping device 114. The piston-cylinder units 184are also operable to release the shoulder screws 186 and the washers 190from contact with the carriage 148 so that the carriage is free to move,rotate or pivot relative to the bearing block 146. When the shoulderscrews 186 and, thus, the washers 190 are released from contact with thecarriage 148, the piston-cylinder units 184 end the shoulder screws 186may allow compressed air to leak or bleed into the interface between thecarriage 148 and the bearing block 146 to form, in effect, an airbearing between the carriage and the bearing block.

To provide clean, dry air to the two pancake-style piston-cylinder units184, the fixture 110 may include a quick connect fitting 180 forconnection to a supply of compressed air (not shown) and an air filterand pressure regulator assembly 182. Air that passes from the fitting180 through the air filter and pressure regulator assembly 182 issupplied to the two pancake-style piston-cylinder units 184.

In use, a core is mounted in the fixture 110 with the tip end portion 16in the second gripping device 114 and the root end portion 14 in thefirst gripping device 112. More specifically, the tip end portion 16 ispositioned with its trailing edge 34 resting against the edge locator128 and with its tip end surface 25 resting against the mounting surfacelocator 130. The clamp mechanism 120 is actuated so that the clamp pad144 is moved into contact with the second mounting surface 22 to clampthe tip end portion 16 against movement relative to the second grippingdevice 114 of the fixture 110. The root end portion 14 of the core 10 isplaced in the first gripping device 112 with its surface 19 opposite thefirst mounting surface 18 resting on and supported by the supportsurface 160 of the cradle 150. The root end portion 14 is alsopositioned between the lateral guide surface 162 and the clamping member166. The clamp arm 168, which has been in its first, upright position,is pivoted into its second, horizontal position with the spring plunger174 in engagement with the first mounting surface 18. The half-turnscrew member 176 is twisted into its first position to hold the clamparm 168 in its second, horizontal position. The shoulder screws 186 areloosened.

The core 10 is now able to assume an unstressed or unflexed conditionfree of any stress or deflection imposed by the fixture 110. Inparticular, the carriage 148 and the cradle 150 of the first grippingdevice 112, together with the root end portion 14 of the core 10 held inthe cradle, are ail free to rotate relative to the second grippingdevice 114 and the tip end portion 16 of the core in response to thetwist or other shape inherent in the core after being molded and fired.When the root end portion 14 of the core and the first gripping devicehave ceased to move relative to the tip end portion 16 and the secondgripping device 114, which should occur in a few seconds, the shoulderscrews 186 are tightened so that movement between the root end portion14 of the core 10 and the tip end portion 16 and between the first andsecond gripping devices 112 and 114 is no longer possible. Material maynow be removed from the root end portion 14 and, more particularly, fromone or both of the datum pads 20 or from the tip end portion 16 so thatthe core 10, after the removal of the material, may be placed in a diewithout movable core positioning members. The amount of material removedfrom each datum pad 20 may be the same or different from one datum padto the other. The adjusted or modified datum pads 20 will be thesurfaces in engagement with core locating surfaces of core positioningmembers in a pattern forming die.

The amount of material to be removed from and/or added to the firstmounting surface 18 of the root end portion 14 of a core 10 and/or thesecond mounting surface 22 of the tip end portion 16 of the core can bedetermined in various ways. For example, if the dimensions andconfiguration of the core are measured or determined by, for example,scanning the core with a laser-based or a mechanical probe-basedcoordinate measuring machine, the measured dimensions and shape may beused to calculate or determine the amount of material to be removedand/or added through the use, for example, of commercially availablesoftware. The amount of material to be removed from and/or added to thefirst mounting surface 18 and/or the second mounting surface 22 may,however, be determined empirically such that the core 10 will be withina predetermined range of acceptable positions when the core ispositioned in a pattern forming die with the first mounting surface 18in engagement with a core beating surface or surfaces and with thesecond mounting surface 22 in engagement with a core locating surface orsurfaces. The predetermined range of acceptable positions is determinedrelative to a theoretical as-designed or ideal position in the patternforming die of a theoretical, as-designed or ideal core with atheoretical, as-designed or ideal twist along its length.

If the amount of material to be removed from and/or added to the firstmounting surface 18 and/or the second mounting surface 22 is determinedempirically, the empirically-determined criteria for removing materialwill be same for all cores in a group or set of cores, such as an entireproduction run or lot of cores. With particular reference to the core10, the amount of material to be removed from and/or added to the raiseddatum pads 20 of the first mounting surface 18 will the amount needed tobring each datum pad to an empirically determined level or height abovethe support surface 160 of the cradle 150, on which the surface 19 ofthe root end portion 14 of the core 10 is supported. Because the datumpads 20 that have been adjusted or modified by the removal and/oraddition of material will be the surfaces in engagement with corelocating surfaces of core positioning members in a pattern forming die,the position of the root end portion 14 of the core 10 in the patternforming die will have been established. Because the second mountingsurface 22 of the tip end portion 16 of the core 10 will be the onlyother surface in engagement with core locating surfaces of corepositioning members in the pattern forming die, and because the core hasbeen allowed to assume an unflexed or unstressed condition prior toremoval of material from the datum pads 20, the position of the tip endportion of the core, together with the overall position of the core, inthe pattern forming die will have been established.

The determined amount or depth of material to be removed and/or added tobring the datum pads 20 to a determined height or level above thesupport surface 160 of the cradle 150 may be communicated to and used bya CNC machine to remove, for example, by grinding or sanding, thedetermined amount of material from the datum pads of the first mountingsurface 18. More specifically, the fixture 110 in which a core has beenplaced is itself positioned in a location and orientation in which thedetermined amount of material can be removed by simply causing a tool,such a grinding or sanding tool, to move along a predetermined path. Thematerial removal tool (not shown) may be both moved and operated by amachine, such as, for example, a CNC machine, or may be moved by anindividual with the aid of a guide or jig. If the first mounting surface18 does not have any raised datum pad 20, material may be removeddirectly from the first mounting surface. Alternatively, if the firstmounting surface 18 has depressions (not shown) with bottom surfacesbelow the level of the remainder of the first mounting surface, apredetermined amount or depth of material may be added to thedepressions so as to raise the level of the bottom surfaces of thedepressions, which will be the surfaces in engagement with core locatingsurface of core positioning members in a pattern forming die. The addedmaterial may be a liquid that will quickly dry or harden and may be aplastic material.

After material has been removed from or added to an actual core 10, thecore may be placed in a die, such as the die 60 a of FIG. 11. The die60a is similar in construction and operation to the die 60 of FIG. 6,but lacks the movable core positioning members 78 and associated motorsand drive trains 84 of the die 60 of FIG. 6. In the die 60 a, there arenot lines or rows of movable core positioning members 78 that supped theairfoil portion 26 of the core 10, but rather only two fixed corepositioning members 78 a located adjacent the left end of the die 60 a,as viewed in FIG. 11, and two additional fixed core positioning members78 b located adjacent the right end of the die 60 a. The corepositioning members 78 a are identical in shape to the core positioningmembers 78 of FIG. 6. The core positioning members 78 a are located,however, so that their respective core locating surfaces 80 a engage thetip end portion 16 of the core 10, rather than the airfoil portion 26,and, more particularly, the second mounting surface 22 of the tip endportion. The core positioning members 78 b have L-shaped core locatingsurfaces 80 b so that the core locating surfaces 80 b are capable ofpositioning the core 10 in both in a vertical direction relative to thefirst die surface 66 a of the first die section 62 a and in a lateraldirection relative to the first die surface 66 a. The lateral orhorizontal portions of the core locating surfaces 80 b engage the rootend portion 14 of a core, such as the core 10, and, more particularly,the datum pads 20 of the first mounting surface 18 of the root endportion 14. The core positioning members 78 b may be in the form ofplastic chaplets that can melt into or otherwise be incorporated into apattern, such as the pattern 12.

The die 60 a of FIG. 11 may also include optional pins or core supportmembers 79 in the first die section 62 a, which do not engage a core,such as the core 10, when it is initially positioned in the first diesection. The core support members 79 engage the core 10 in the event ofslight deflection of the core. In particular, the core support members79 may engage and be effective to help support the core 10 if there isdeflection of one or more portions of the core during the injection ofwax 72 into the die 60. The core support members 79 thus may limit therange of deflection of the core 10.

Also shown in FIG. 11 is the lower half of a passage 96 for conductingwax 72 into the die 60 a when the die is closed. The lower half of thepassage 96 is formed in the first die section 62 a and the upper half(not shown) of the passage is formed in the second die section (notshown). The passage 96 is completed when the second die section (notshown) is moved into contact with the first die section 62 a, and thedie 60 a is thus closed. The passage 96 has an inlet 98 through whichwax 72 is injected into the passage.

FIG. 12 is a flow chart detailing a process or method 300 of forming acasting mold pattern that includes a core. The pattern may be a patternsuch as pattern 12, as shown in FIGS. 3 and 4. Similarly, the core maybe a core such as the core 10, as shown in FIGS. 1-6. The method of FIG.12 involves the use of a die, such as die 60 or die 60 a, and a fixture,such as fixture 110.

The method 300 starts at block 310. The method 300 then proceeds to step312, in which a core, such as the core 10, is mounted in a fixture, suchas the fixture 110. The fixture has a first gripping device and a secondgripping device. The first gripping device is spaced apart from thefirst gripping device and is free to rotate relative to the secondgripping device. The core is mounted in the fixture with the firstgripping device gripping the core adjacent a first end of the core andwith the second gripping device gripping the core adjacent a second endof the core.

At step 314, the first gripping device and the first end of the core arepermitted to rotate freely relative to the second gripping device andthe second end of the core so that the core is free of any twistingalong the length of the core imposed by the fixture. After the firstgripping device and the first end of the core have been allowed torotate relative to the second gripping device and the second end of thecore, the method proceeds to step 316 in which the first gripping deviceis locked against rotation relative to the second gripping device.

The method 300 next proceeds to step 318, in which material is removedfrom and/or added to either or both a first mounting surface and asecond mounting surface so that the core will be within a predeterminedrange of acceptable positions relative to a position of a theoretical,as-designed or ideal core when the core is positioned in a die. Afterstep 318, the next step 320 of the method 300 is positioning the core ina die that has at least one first core locating surface to support thefirst end of the core and at least one second core locating surface tosupport the second end of the core. The first mounting surface of thecore is positioned in engagement with the first core locating surface orsurfaces of the die, and the second mounting surface of the core ispositioned in engagement with the second core locating surface orsurfaces of the die. Lastly, the method 300 proceeds to step 322, inwhich a flow of wax is conducted into the die while the core is inengagement with the first and second core locating surfaces. When thewax hardens, the casting mold pattern has been formed.

Although the core 10 has been described as having a first mountingsurface 18 with two raised datum pads 20 that effectively function astwo mounting surfaces, the first mounting surface may not have anyraised datum pads. The first mounting surface 18 may alternatively havemore or fewer than two raised datum pads 20 or may have depressions withbottom surfaces below the level of the remainder of the first mountingsurface. If the first mounting surface 13 is formed with depressionshaving bottom surfaces below the level of the remainder of the firstmounting surface, the depressions would be filled in as required toimplement the present invention. Also, while the core 10 and the methodof using the core 10 to form the casting mold pattern 12 have beendescribed with particular reference to adjusting or removing materialfrom the first mounting surface 18 or potentially adding material to thefirst mounting surface, the core may be formed and the method may beimplemented by adjusting or removing material from or adding material tothe second mounting surface 22 or from or to both the first mountingsurface 18 and the second mounting surface 22. Further, although thelooking device has been shown and described as comprising two shoulderscrews 186 operable by piston-cylinder units 184, the locking devicecould comprise a variety of other structures. For example, instead oftwo shoulder screws 186, the locking device could comprise two shaftsthat are each threaded at one end to receive a wing nut, which would betightened against the surface 192 of the carriage 148. The lockingdevice might alternatively comprise a clamping mechanism, such as a setscrew, for engaging the curved outer surface 158 of the carriage 148.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. Suchimprovements, changes, and/or modifications within the skill of the artare intended to be covered by the appended claims.

Having described the invention, the following is claimed:
 1. A method offorming a casting mold pattern that includes a core, the core having alength, a first end, and a second end, the second end being spaced apartfrom the first end by the length, the core also having a first mountingsurface adjacent the first end of the core and a second mounting surfaceadjacent the second end of the core, said method comprising the stepsof: (a) removing material from and/or adding material to the firstmounting surface and/or the second mounting surface: (b) positioning thecore in a pattern forming die alter removing material from and/or addingmaterial to the first mounting surface and/or the second mountingsurface, the pattern forming die having a first core locating surface tosupport the first end of the core and a second core locating surface tosupport the second end of the core, the core being positioned in thepattern forming die with the first mounting surface in engagement withthe first core locating surface and with the second mounting surface inengagement with the second core locating surface; and (c) conducting aflow of wax into the pattern forming die to form a casting mold patternwhile the core is positioned in the pattern forming die with the firstmounting surface in engagement with the first core locating surface andwith the second mounting surface in engagement with the second corelocating surface, the material being removed from and/or added to thefirst mounting surface and/or the second mounting surface being in anamount such that the core will be within a predetermined range ofacceptable positions when the core is positioned in the pattern formingdie with the first mounting surface in engagement with the first corelocating surface and with the second mounting surface in engagement withthe second core locating surface, the predetermined range of acceptablepositions being determined relative to an ideal position in the patternforming die of an ideal core.
 2. The method of claim 1 furthercomprising the step of supporting the core such that the core is free ofexternally applied flexing, the step of removing material from and/oradding material to the first mounting surface and/or the second mountingsurface including removing material from and/or adding material to thefirst mounting surface and/or the second mounting surface whilesupporting the core such that the core is free of externally appliedflexing.
 3. The method of claim 2 wherein the step of supporting thecore such that the core is free of externally applied flexing comprisesmounting the core in a fixture such that the core is free of flexingalong the length of the core imposed by the fixture.
 4. The method ofclaim 3 wherein the fixture has a first gripping device and a secondgripping device, the first gripping device being spaced apart from thesecond gripping device and being able to rotate relative to the secondgripping device, the step of mounting the core in a fixture including(i) mounting the core with the first gripping device gripping the coreadjacent the first end and with the second gripping device gripping thecore adjacent the second end and (ii) permitting the first grippingdevice and the first end of the core to rotate relative to the secondgripping device and the second end of the core so that the core is freeof flexing along the length of the core imposed by the fixture.
 5. Themethod of claim 4 also comprising the step of locking the first grippingdevice against rotation relative to the second gripping device after thefirst gripping device and the first end of the core have been allowed torotate relative to the second gripping device and the second end of thecore.
 6. The method of claim 1 wherein the core has a twist along itslength
 7. The method of claim 1 wherein the first mounting surface isone of a plurality of first mounting surfaces and wherein the first corelocating surface is one of a plurality of first core locating surfaces,the step of positioning the core in a pattern forming die includingpositioning the plurality of first mounting surfaces in engagement withthe plurality of first core locating surfaces.
 8. The method of claim 1wherein the core has a convex major side surface extending from a tipend portion of the core to a root end portion of the core, the core alsohaving a concave major side surface extending from the tip end portionof the core to the root end portion of the core, the concave major sidesurface being spaced apart from and presented in a direction away fromthe convex major side surface.
 9. The method of claim 1 wherein the coreis molded from a ceramic material and fired at an elevated temperaturebefore removing material from and/or adding material to the firstmounting surface and/or the second mounting surface.
 10. The method ofclaim 1 wherein the pattern forming die includes a first die section anda second die section, the pattern forming die being in a closedcondition to receive and contain the flow of wax when the second diesection is moved toward and into contact with the first die section, thepattern forming die being in an open condition to receive the core whenthe second die section is moved away from and out of contact with thefirst die section.
 11. The method of claim 1 wherein the first andsecond core locating surfaces are fixed in position relative to thepattern forming die.
 12. The method of claim 1 wherein the step ofremoving material from and/or adding material to the first mountingsurface and/or the second mounting surface consists of removing materialfrom the first mounting surface and/or the second mounting surface. 13.A method of adjusting a core to be at least partially covered by wax toproduce a casting mold pattern, the core having a length, a first end,and a second end, the second end being spaced apart from the first endby the length, the core also having a first mounting surface adjacentthe first end of the core and a second mounting surface adjacent thesecond end of the core, said method comprising the steps of: (a)mounting the core in a fixture such that the core is free of flexingalong the length of the core Imposed by the fixture; and (b) removingmaterial from the first mounting surface and/or the second mountingsurface; the material being removed from the first mounting surfaceand/or the second mounting surface being in an amount such that the corewill be within a predetermined range of acceptable positions when thecore is positioned in a pattern forming die with the first mountingsurface in engagement with a first core locating surface of the patternforming die and with the second mounting surface in engagement with asecond core locating surface of the pattern forming die, thepredetermined range of acceptable positions being determined relative toan ideal position in the pattern forming die of an ideal core.
 14. Themethod of claim 13 wherein the fixture has a first gripping device and asecond gripping device, the first gripping device being spaced apartfrom the second gripping device and being able to rotate relative to thesecond gripping device, the step of mounting the core in a fixtureincluding (i) mounting the core with the first gripping device grippingthe core adjacent the first end and with the second gripping devicegripping the core adjacent the second end and (ii) permitting the firstgripping device and the first end of the core to rotate relative to thesecond gripping device and the second end of the core so that the coreis free of flexing along the length of the core Imposed by the fixture.15. The method of claim 14 also comprising the step of locking the firstgripping device against rotation relative to the second gripping deviceafter the first gripping device and the first end of the core have beenallowed to rotate relative to the second gripping device and the secondend of the core.
 16. The method of claim 13 wherein the core has aconvex major side surface extending from a tip end portion of the coreto a root end portion of the core, the core also having a concave majorside surface extending from the tip end portion of the core to the rootend portion of the core, the convex major side surface being spacedapart from and presented in a direction away horn the concave major sidesurface.
 17. The method of claim 13 wherein the core is molded from aceramic material and fired at an elevated temperature before beingmounted in the fixture.
 18. A fixture for adjusting a core to be atleast partially covered by wax to produce a casting mold pattern, thecore having a length, a first end, and a second end, the second endbeing spaced apart from the first end by the length, the core alsohaving a first mounting surface adjacent the first end of the core and asecond mounting surface adjacent the second end of the core, saidfixture comprising: (a) a first gripping device configured anddimensioned to grip the core adjacent its first end; (b) a secondgripping device configured and dimensioned to grip the core adjacent itssecond end, the first gripping device being spaced apart from the secondgripping device and being able to rotate relative to the second grippingdevice; and (c) a locking device for locking the first gripping deviceagainst rotation relative to the second gripping device.
 19. The fixtureof claim 13 wherein the first gripping device includes (i) a supportthat maintains a fixed rotational position relative to the secondgripping device, and (ii) a carriage pivotally mounted on the supportfor pivotal movement relative to the support and the second grippingdevice, the locking device locking the carriage against pivotal movementrelative to the support and the second gripping device.
 20. The fixtureof claim 19 wherein the first gripping device also includes a supportsurface carried by the carriage for engaging and supporting a surface ofthe core opposite the first mounting surface.